Figure 19. Panel "d": Displays of distributions for P. edulis, P. engelmannii, P. banksiana, and P. clausa in relation to the three bioclimatic variables. In this figure, each of the four boxes represents approximately 25 percent of the grid points in North America in relation to the moisture index (see caption for fig. 14 for explanation), ranging from the driest quartile on the left to the wettest quartile on the right. Within each box the mean temperature of the coldest month is arrayed on the vertical axis and growing degree days (5°C base) on the horizontal axis.
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